DALAN CHAPARA, India—Lalasa Devi says that before her attacker grabbed her by the throat, he snarled "Chamar," the name of the so-called untouchable caste into which she was born. "What can you do to me?"

Then he threw her to the ground and raped her, she says.

Ms. Devi, a mother of four in her mid-30s, says authorities treated her poorly when she registered a complaint against her alleged assailant, who...